Clinical studies suggest combined insulin-sulfonylurea therapy may yield less glycemic variability than insulin alone. This CRC protocol studies this concept by comparing the two regimens with respect to 1) glycemic variability over 24 hours, and 2) tendency to hypoglycemia with fasting plus mild exercise. Ten subjects will be studied in a crossover design, with two 3-day stays in the CRC. Less glycemic variability and less tendency to become hypoglycemic with combined therapy would support the use of this.